CVS 1 (Basics) Flashcards
Which side of the heart (left/right) pumps blood from the body to the lungs?
Right heart
The left heart pumps blood from where to where?
Lungs to body
Why does the heart wall require its own blood supply?
Heart wall is thick, and diffusion from chambers would take too long
Describe the capillary wall:
Single endothelial cell thick, surrounded by basal lamina
What is required for diffusion of gases to occur?
Concentration gradient
Rate of diffusion depend on:
- Surface area available for diffusion
- Diffusion resistance (nature of molecule/barrier, and path length)
- Concentration gradient
How does capillary density differ between tissues?
A more metabolically active tissue will have higher capillary density than a less metabolically active tissue
In the body, what maintains the concentration gradient of substances used by tissues?
Blood flow
Define perfusion rate:
Rate of blood flow to capillary bed
What are the units given to describe blood flow in the body to tissues?
ml/min/g
What is the blood flow required by the brain?
0.5 ml/min/g
What is the blood flow required by the heart at rest?
0.9 ml/min/g
What is the blood flow required by the kidneys?
3.5 ml/min/g
What is the minimum total blood flow around a typical 70kg man in L/min?
5 L/min
What is the maximum total blood flow around a typical 70kg man in L/min?
25 L/min
What are the 2 main ways of controlling flow through the CVS?
1) Arterioles
2) Pre-capillary sphincters
Why is the brain one of the hardest-to-perfuse areas of the body?
Gravity
What part of the CVS acts as a variable reservoir of blood, allowing the total flow in the system to change?
Veins
What characteristics of veins allow them to act as variable reservoirs of blood?
Thin elastic walls that can easily distend or collapse
Approximately what percentage of the bodies blood is in the venous system at any time?
~ 67%
Approximately what percentage of the bodies blood is in the artery/arteriole system at any time?
~ 11%
Approximately what percentage of the bodies blood is in the capillary system at any time?
~ 5%
Approximately what percentage of the bodies blood is in the heart/lungs at any time?
~ 17%
Describe the layers of the pericardial sac:
3 layers:
- Outer fibrous layer
- Parietal serous layer, connected to fibrous layer
- Visceral serous layer, connected to myocardium
How many liters of blood does the heart pump on average per minute (at rest)?
~ 5 L/min
What is the name given to the vessels joining arterioles to capillaries?
Metarterioles
What is the name given to the vessels joining capillaries to venules?
Post-capillary venules
In which blood vessel is the blood flow at the highest velocity?
Aorta
Name the 3 elastic arteries which branch from the aortic arch, in order from nearest to the heart:
1) Brachiocephalic
2) Left common carotid
3) Left subclavian
How many pulmonary veins feed into the left atrium?
4
The descending aorta bifurcates in the abdominal cavity, into which 2 main arteries?
Left and right common Iliac arteries
There are 8 main elastic arteries of the body. Name them:
1) Left pulmonary
2) Right pulmonary
3) Aorta
4) Brachiocephalic
5) Left common carotid
6) Left subclavian
7) Left common Iliac
8) Right common Iliac
What is the normal range of blood pressure?
90/60 - 120/90 mmHg
How does the aorta maintain pressure during diastole?
Elastic walls recoil
In which type of blood vessel does the blood pressure change from being pulsatile to constant?
Arterioles
What are the 3 major types of arteries, in order from largest to smallest?
1) Elastic conducting
2) Muscular distributing
3) Arterioles
What are the 3 layers of arteries and veins, from innermost to outermost?
1) Tunica intima
2) Tunica media
3) Tunica adventitia
Why may elastic arteries appear yellow when fresh?
Due to abundant elastin
What colour does elastin appear when fresh (unstained/fixed)?
Yellow
What colour does elastin appear when fixed?
White
Define ‘vasa vasorum’:
‘Vessels of vessels’ = blood vessels of large blood vessels
In the tunica media of an artery, what cells produce the elastic, collagen and matrix?
Smooth muscle cells
What is meant by ‘dissection of the aorta’, and what causes it?
When blood escapes from the lumen of the aorta, through a tear, creating a space between the tunica intima and tunica media. This blood clots and distorts the aorta, increasing pressure further.
Caused by high internal pressure of blood flow
Define ‘end artery’:
Terminal artery supplying all or most of the blood to a body part without significant collateral circulation
Give 2 examples of absolute end arteries:
1) Central artery to retina
2) Labyrinthine artery of internal ear
What is myocardial bridging?
When a layer of myocardium lies over a coronary artery rather than under it.
What is the name given to the condition where a layer of myocardium lies over a coronary artery rather than under it?
Myocardial bridging
Why is myocardial bridging usually asymptomatic?
Because the coronary arteries usually fill during diastole
What is the name given to arteries which supply blood to the capillary beds?
Metarterioles
What is the difference between arterioles and metarterioles?
Arterioles - continuous smooth muscle layer
Metarterioles - non-continuous smooth muscle layer (smooth muscle cell = pre-capillary sphincters)
What cell type makes up the tunica adventitia of an arteriole?
Fibroblasts
Why is it important for blood to flow at its slowest velocity through capillaries?
To allow time for gas/nutrient-exchange to take place
What is the approx. diameter of a capillary?
~ 7-10 um
What are the 3 types of capillaries?
1) Continuous
2) Fenestrated
3) Sinusoidal (discontinuous)
What is the most common type of capillary?
Continuous capillary
What junction type joins the endothelial cells in capillaries?
Tight junctions
What is the name given to the smooth muscle cells encircling the endothelium of a capillary arising from a metarteriole?
Pre-capillary sphincter
What is the importance of a pre-capillary sphincter?
Allows regulation of blood flow to capillary bed
Via which passage could blood bypass the capillary bed?
Via the central channel: metarteriole and throughfare channel
What is the importance of the ‘central channel’ through capillary beds?
It allows blood to bypass the capillaries, and consists of a metarteriole and throughfare channel
Where does lymphatic fluid drain into the blood?
- Left subclavian vein (mostly)
- Right subclavian vein (R head, trunk, arm)
If all pre-capillary sphincters of a capillary bed were shut, where would blood flow?
Through the central channel (metarteriole and throughfare channel) which bypasses the capillary bed, into the post-capillary venule
Approximately how much fluid does the lymphatic system drain per hour? (ml/hr)
100 ml/hr
On average what percentage of our total blood volume is held in our capillaries at any one time?
~ 5%
In what blood vessel is blood flow at its slowest velocity?
Capillaries
What does a capillary wall consist of?
- Endothelium
- Basement membrane
Where are continuous capillaries found?
- Nervous tissue
- Connective tissue
- Muscle tissue
- Exocrine glands
- Lungs
Where are fenestrated capillaries found?
- Endocrine glands
- Parts of gut
- Renal glomerulus
Where are sinusoidal/discontinuous capillaries found?
- Liver
- Spleen
- Bone marrow
Which type of capillary has the largest diameter?
Sinusoidal/discontinuous capillaries
What is the main function of a sinusoidal/discontinuous capillary?
Has large gaps in its walls, allowing cells to move between the blood and tissue.
Which cell type form a branching network on the outer surface of the endothelium of capillaries?
Pericytes
What are pericytes?
Cells which form a branching network on the outer surface of the endothelium of capillaries. They are pluripotent and can differentiate into muscle cells or fibroblasts.
What are the 4 possible routes of transport across the endothelial wall of a fenestrated capillary?
1) Diffusion across cell
2) Transcytosis
3) Diffusion via intercellular cleft
4) Diffusion via fenestration
Which capillary type has an incomplete basement membrane?
Sinusoidal/discontinuous capillaries
